-- validate lock tuple trigger
\set ON_ERROR_STOP 1
CREATE EXTENSION tuplock;
-- test in a distinct schema...
CREATE SCHEMA test_tuplock;
SET search_path TO test_tuplock,public;
CREATE TABLE test(
  tid SERIAL PRIMARY KEY,
  data TEXT NOT NULL,
  -- locking attribute
  lock BOOLEAN NOT NULL DEFAULT FALSE
);
CREATE TRIGGER testlock
BEFORE UPDATE OR DELETE ON test
FOR EACH ROW EXECUTE PROCEDURE tuplock(lock);
SELECT COUNT(*) FROM test; -- 0
 count 
-------
     0
(1 row)

-- first insert new values
INSERT INTO test(data) VALUES('hello');
INSERT INTO test(data) VALUES('world');
INSERT INTO test(data) VALUES('!');
INSERT INTO test(data) VALUES('foo');
INSERT INTO test(data) VALUES('bla');
-- show all
SELECT * FROM test ORDER BY tid;
 tid | data  | lock 
-----+-------+------
   1 | hello | f
   2 | world | f
   3 | !     | f
   4 | foo   | f
   5 | bla   | f
(5 rows)

-- update is fine
UPDATE test SET data='HELLO' WHERE data='hello';
-- delete is fine
DELETE FROM test WHERE data='!';
-- then lock
UPDATE test SET lock=TRUE WHERE lock=FALSE AND length(data)<>3;
-- errors are fine, now:
\set ON_ERROR_STOP 0
-- now updates are not ok
UPDATE test SET data='WORLD' WHERE data='world'; -- fails
ERROR:  trigger "testlock" on "test": item locked by attribute "lock"
UPDATE test SET lock=FALSE; -- fails
ERROR:  trigger "testlock" on "test": item locked by attribute "lock"
-- now deletes are not ok
DELETE FROM test WHERE data='HELLO'; -- fails
ERROR:  trigger "testlock" on "test": item locked by attribute "lock"
-- back to normal
\set ON_ERROR_STOP 1
-- this update is ok
UPDATE test SET data='FOO' WHERE data='foo';
-- this delete is ok
DELETE FROM test WHERE data='bla';
-- show all
SELECT * FROM test ORDER BY tid;
 tid | data  | lock 
-----+-------+------
   1 | HELLO | t
   2 | world | t
   4 | FOO   | f
(3 rows)

-- clean
DROP SCHEMA test_tuplock CASCADE;